1. Field of the Invention
The present invention relates to a thermoplastic elastomer composition, a molded article obtained by using the thermoplastic elastomer composition and an ethylene-xcex1-olefin copolymer. More specifically, the present invention relates to a thermoplastic elastomer composition which has excellent flexibility and processability, manifests no bleed of low molecular weight components, and particularly excellent in extrusion processability and calender processability, an extrusion molded article obtained by extrusion molding the thermoplastic elastomer composition or a calender molded article obtained by calender molding the thermoplastic elastomer composition, and an ethylene-xcex1-olefin copolymer.
2. Description of Related Art
Soft vinyl chloride materials having good balance between mechanical strength and flexibility are a material excellent in processability and cost performance. However, the use thereof is restricted due to recent environmental problems. On the other hand, an ethylene-xcex1-olefin copolymer rubber can be listed as the polyolefin-based material excellent in recycling property. The ethylene-xcex1-olefin copolymer rubber is used widely as an automobile material, construction material, wire material and polyolefin-modifying material, together with ethylene-xcex1-olefin-non-conjugated diene rubber such as EPDM and the like. In these uses, excellent processability, particularly excellent roll processability and excellent extrusion processability are required in addition to excellent vulcanization property. From this standpoint, an ethylene-xcex1-olefin-non-conjugated diene rubber such as EPDM and the like having excellent processability by inclusion of a diene component is used more widely than ethylene-xcex1-olefin copolymer rubber. As the conventional technology for further improving processability, there is a method in which ethylene-xcex1-olefin-non-conjugated diene rubber having wider molecular weight distribution is produced by using a special catalyst such as a vanadate of secondary alcohol and the like as disclosed, for example, in Japanese Patent Application Laid-Open (JP-A) No. 61-4708. Further, Japanese Patent Application Publication (JP-B) No. 6-18942 discloses a rubber composition obtained by compounding a vulcanized rubber compounding agent into ethylene-xcex1-olefin-non-conjugated diene copolymer rubber having wide molecular weight distribution. The rubber containing a diene component has excellent processability, but may cause a problem of remaining of odor in the final product since this rubber contains a diene monomer odor as compared with rubber containing no diene component.
Further, JP-A No. 9-241325 discloses an ethylene-xcex1-olefin copolymer rubber which has excellent processability, heat-resistance and high tensile strength, causes no bleed in low molecular weight parts, and has a specific composition, molecular weight and molecular weight distribution. However, in view of recent further strict quality requirements, this method include problems that prevention of bleed is insufficient, the surface appearance of the final product using the above-mentioned copolymer is degraded, further, pellets of the copolymer adhere each other under a slight load and small block form can not be maintained for a long period of time, workability and handling such as transportation and measurement in compounding into a polyolefin-based resin are insufficient.
The present inventors have intensively studied a thermoplastic elastomer composition having no above-mentioned problems, and found that a thermoplastic elastomer composition comprising a specific ethylene-xcex1-olefin copolymer and a specific polyolefin-based resin is excellent in extrusion processability and calender processability, and gives excellent flexibility and processability, and manifests no bleed of low molecular weight components when made into an extrusion molded article or calender-molded article, and have completed the present invention.
Namely, the present invention relates to a thermoplastic elastomer composition comprising 5 to 95 wt % of the following (A) and 5 to 95 wt % of the following (B), wherein the flowability index I according to a test for flow properties with a capillary rheometer is 1.35 or more:
(A) an ethylene-xcex1-olefin copolymer having a tensile stress M100 measured according to JIS-K-6251 of 2.5 MPa or less,
(B) a polyolefin-based resin having a tensile stress M100 measured according to JIS-K-6251 of 2.5 MPa or more.